1. Field of the Invention
The invention relates to polymeric materials that undergo transition-metal catalyzed olefin metathesis reactions.
2. Related Art
Introducing self-healing capability into materials would greatly improve their safety feature, lifetime, and energy efficiency. A significant amount of efforts has been devoted to this field in recent years and several groups have reported different self-healing polymer designs through the incorporation of encapsulated monomers (1,2) dynamic non-covalent bonding, (3-12) and reversible (13-25) or irreversible (26,27) covalent bonds into polymers. Recently, dynamic covalent chemistry (28,29)—such as thermal (13-15) and light-catalyzed cycloaddition, (16,17,30) transesterification, (18,31) radical reactions, (19-21,32) thiol-disulfide exchange, (22) hydrazone formation (23,24) and siloxane equilibration (25)—have attracted much attention for their applications in self-healing or malleable polymer designs.
Most dynamic covalent bonds used for self-healing applications involve heteroatoms in dynamic exchange reactions. (18,19,22,23,25) In principle, reversible carbon-carbon (C—C) bond formation should be particularly attractive for such applications because the high stability of C—C bonds may offer the possibility of designing stronger self-healing materials. Among the few examples of dynamic C—C bond-based self-healing polymers, those involving strong C—C bonds, such as reversible Diels-Alder reactions (13) and photochemical cycloaddition reactions, (16,17,30) require substantial inputs of external energy in the form of heat or light to trigger the reversible C—C bond formation. On the other hand, the one using weak dynamic C—C bond, while can self-heal without providing external energy, only results in relatively weak self-healing polymer gels. (20) In addition, most of those self-healing systems require specially designed monomers or polymers to serve the purpose. It would be highly desirable to develop a simple strategy for effective polymer healing through dynamic exchange of strong C═C bond under ambient conditions.